In healthy conditions, articular cartilage forms a smooth surface between articulating bone ends to reduce the friction caused by movement. This friction is further reduced by the synovial fluid.
Articular cartilage consists of chondrocytes and two major macro-molecules; i.e., collagen and proteoglycans, which are synthesized by and deposited around the chondrocytes. The chondrocytes also synthesize the synovial fluid which bathes the articular cartilage.
The structural integrity of the articular cartilage is the foundation of optimal functioning of the skeletal joints in the hip, shoulders, elbows, hocks and stifles. Impaired function of skeletal joints will dramatically reduce mobility such as rising from sitting position or climbing and descending stairs.
To maintain the structural integrity and the proper functioning of the articular cartilage, the chondrocytes constantly synthesize collagen and proteoglycans, the major components of the articular cartilage, as well as the friction-reducing synovial fluid. This constant synthesis of the macro-molecules and synovial fluid provides the articular cartilage with the repairing mechanism for most of the wearing caused by friction between the bone ends. However, it also leads to the constant demand for the supply of precursors, or building blocks, for the macromolecules and synovial fluid. Lack of this precursors will lead to defects in the structure and function of the skeletal joints. This deficiency occurs often when activity levels are very high, or cartilage tissue has been traumatized.
An adequate supply of metabolic precursors or building blocks is thus paramount to replacement and repair of the constituents of skeletal joints, connective tissue and synovial fluid. Proteoglycans (or mucopolysaccharides) form the ground substance of cartilage, bone and joint fluid. Proteoglycans are comprised of proteins linked to glycosaminoglycans (GAGs). The building block GAG subunit of the proteoglycan in cartilage and bone is chondroitin sulfate. Chondroitin sulfate A is present in cornea and cartilage. Chondroitin sulfate B (G-heparin) is found in tendon, aorta, skin and heart valves. Chondroitin C is found in cartilage, tendon and umbilical cord and similar tissues. The building block GAG subunit of the proteoglycan in joint fluid is hyaluronic acid. Intercellular solutions of hyaluronic acid are viscous and thus assist in lubrication of the joints of body skeleton. Hyaluronic acid is synthesized from the metabolic precursor, glucosamine. The availability of glucosamine in cartilage tissue can be rate-limiting to the enzymatic step leading to the production of proteoglycans. Exogenous glucosamine serves to drive the biosynthetic pathway forward past the rate-limiting blockage point. Glucosamine serves as a substrate for a kinase enzyme which yields glucosamine-6-phosphate, the rate-limiting precursor in proteoglycan synthesis. Recently, studies have reported the suppression of autoimmune disorders such as rheumatoid arthritis upon ingestion of cartilage fibers derived from chickens and sharks. The therapy, termed oral tolerization, is not fully understood but it is theorized that a mechanism in the digestive tract disarms immune cells that would otherwise assault food molecules as foreign intruders to the body, akin to foreign substances that enter the blood stream by means other than the gastrointestinal tract. Apparently, the immune-disarming effect occurs not only in the gut, but also in the vulnerable tissues.
Numerous disclosures describe therapy of damaged tissues by introduction of precursors in the metabolic pathway leading to biosynthesis of the macromolecules of connective tissues. For example, in U.S. Pat. No. 3,697,652 (Rovati et al.), N-acetylglucosamine is used to treat degenerative afflictions of the joints. In U.S. Pat. No. 3,683,076 (Rovati et al.), glucosamine salts are described as pharmaceutically useful for treatment of osteoarthritis and rheumatoid arthritis. U.S. Pat. Nos. 4,647,453 (Meisner) and 4,772,591 (Meisner) disclose the use of glucosamine salts for treatment of degenerative inflammatory disease and as a means of accelerating wound healing. In U.S. Pat. No. 4,801,619 (Lindblad), a hyaluronic acid preparation is claimed to be effective for treatment of steroid arthropathy and progressive cartilage degeneration caused by proteoglycan degradation. A combination of glucosamine, chondroitin and manganese is claimed in U.S. Pat. No. 5,364,845 (Henderson) as a means of protecting and repair of connective tissue. None of these prior investigators, however, disclose a composition having metabolic precursors, herbal phytochemicals and palatability agents that work synergistically to prevent and treat joint and connective tissue disorders.